1. Field of the Invention
The present invention relates to an image forming apparatus, a storage unit controlling method, and a storage unit controlling program product.
2. Description of the Related Art
In an image forming apparatus such as a digital MFP (Multi Function Peripheral) and the like, there is provided an EEPROM (Electrically Erasable Programmable Read-Only Memory) to store count information representing a printing quantity and/or various setting values on a control board. The EEPROM is a non-volatile rewritable memory and has a rewriting limit (lifetime) in its number of times. The rewriting lifetime is approximately a hundred thousand times. On the other hand, the upper limit of the printing quantity in the MFP is approximately a million and half shetts. Thus, if the printing quantity such as monochrome printing quantity or color printing quantity is counted by the EEPROM which is mounted on the control board of the MFP main body, the upper limit of the printing quantity in the MFP exceeds the rewriting lifetime of the EEPROM.
In order to address the aforementioned problem, there is provided a method of averaging and thereby limiting the rewriting in its number of times for each address, resulting in the improved lifetime of the EEPROM device. However, this method of limiting the number of times still has the problems that (i) the lifetime of the EEPROM mounted on the control board of the MFP main body becomes shorter, since the printing quantity is counted only by the EEPROM of the control board of the MFP main body and the rewriting increases in its frequency, (ii) a large capacity EEPROM is required in order to reduce the rewriting rotation frequency, (iii) the replacement of the control board is required when recycling the MFP main body, since the lifetime of the EEPROM ends when recycling the control board [sic], and (iv) the averaging effect cannot be obtained in a case that the rewriting number of times is the same for all the addresses.
The invention disclosed in Japanese Patent Application Laid-open No. 2007-248538 is known as a technology to cope with these problems. In this invention, an EEPROM attached to a toner bottle is used. Namely, apart from an EEPROM mounted on a control board of an MFP main body, each toner bottle is provided with an EEPROM; the EEPROM mounted on the control board records thereon the counted number of copies made in the MFP main body, and the EEPROM attached to each toner bottle records thereon the counted number of copies made by use of toner in the toner bottle. To extend the life of the EEPROM attached to each color toner bottle, not at the end of job but at the time of replacement of the toner bottle, data on the number of copies recorded on the EEPROM mounted on the control board is written on the EEPROM attached to the toner bottle. This reduces the number of times the EEPROM attached to the toner bottle is rewritten, thereby extending the life of the EEPROM.
However, the invention disclosed in Japanese Patent Application Laid-open No. 2007-248538 can extend the life of the EEPROM attached to the toner bottle, but the above-described problems (i) and (iii) are not resolved, that is, the life of the EEPROM mounted on the control board of the MFP main body is still short, so a large-capacity EEPROM needs to be mounted or the EEPROM needs to be replaced at the time of recycling of the MFP main body.